I understand that upgrading hardware and operating systems is expensive but why make it worse by adding hosting a bitcoin node as one of the functions that this server performs?
Hopefully you aren't storing more than two bitcoins on that box.
I know I should, but I just don't have the time to migrate everything to a new system. With some luck I can do it in my next vacation.
No and even if/when they exist you will only be able to prune spent outputs.
Even that would compact the blockchain nicely.
This doesn't quite answer your question, but you only need to back up the wallet.dat file, which should be quite small. The rest could be downloaded again from the network if lost.
True, but it would take really long for me, so adding the blockchain to the backup is the fastet restore option.